using System;
 
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            var myClass = new MyClass();
            //мы можем написать свой делегат, потому что нам доступен тип
            myClass.SetMyClass2Creater(() => new MyClass.MyClass2());
		}
    }
}
 
internal class MyClass
{
    private Func<MyClass2> Creater;
 
    public void SetMyClass2Creater(Func<MyClass2> creater)
    {
        Creater = creater;
    }
 
    public class MyClass2
    {
 
    }
}

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